I tend to prefer a mass attached to a spring slidiing a frictionless surface for the RC circuit analogy. Somehow the inductance/mass and capacitance/spring constant analogies seem more intuitive to me than inductance/length of string and capacitance/g. I suppose it makes adding a resistor a bit harder, since the idea of a velocity dependent frictional force is likely to be pretty foreign to them, but nicer for the basic one in my mind.